Method for the local heating of metallic work-pieces by inductive hf-heating and hf-inductor



March 1957 D c. AN IPEREN 785,263

V METHOD FOR THE LOCAL HEATING OF METALLIC WORK-PIECES BY INDUCTIVE HF-HEATING AND HF-INDUCTOR Filed Jan. 29, 1953 !NVENTOR DlRK CHRISTIAAN VAN IPEREN AGENT United States Patent METHOD FOR THE LOCAL HEATING OF METAL- LIC WORK-PIECES BY INDUCTEVE EF HEA'I- ING AND HF-INDUCTOR Dirk Christiaan van Iperen, Eindhoven, Netherlands, as-

signor, by mesne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application January 29, 1953, Serial No. 334,045

Claims priority, application Netherlands March 28, 1952 3 Claims. (Cl. 219-1041) From French patent specification 971,038 a method is known for the local heating of metallic work-pieces by inductive HF-heating with the use of an inductor comprising a core which is U-shaped at least in part and which may be manufactured from material having a high electric resistance at high frequencies, preferably ferrite, the core being arranged with respect to the workpiece in such manner that in practice a closed magnetic circuit is formed, the core and the work-piece performing a movement relatively to one another. in the said French patent specification the work-piece is turned with respect to the core about a shaft, so that a circular part of the work-piece is heated between the limbs of the U-shaped core.

The invention is based on recognition of the fact that the above-mentioned method may also be carried out in a different manner, which opens a larger range of application.

According to the invention, for this purpose the relative movement is carried out in such manner that the heating zone on the work-piece constitutes a desired path.

The direction of the said path preferably makes an angle, more particularly of 90, with the plane passing through the U-shape of the core.

According to a further feature of the invention, the heated part of the Work-piece in the vicinity of the core is provided with soldering material, which is important inter alia for the tin industry.

The invention furthermore relates to an HF-inductor which comprises a core, at least partly U-shaped, of the above-mentioned material and which, if desired, may be cooled artificially, and it is characterised in that the inductor is combined with a holder for soldering material to form an assembly.

In order that the invention may be readily carried into effect, it will now be described with reference to the accompanying drawing, given by Way of example.

Figs. 1, 2 and 3 show a vertical section, a side-view and a horizontal section respectively of an inductor 1 and a U-shaped core 2 which, together with a workpiece 3, substantially constitutes a closed magnetic circuit. If the work-piece is moved in the direction of arrow 4 in Fig. 3, a heating zone 5 provided between the limbs of the U-shaped core 2 traverses a path 6 (see Fig. 3). Since in this case the left-hand limb 7 (see Fig. 1) is invariably above a portion of the path which has just been heated, this limb is subject to additional heating. Consequently, it is preferable that the workpiece 3 should be pulled along in the direction of arrow 8, so that the heating zone traverses a path 9 and the above-mentioned additional heating is either suppressed or takes place to an inappreciable extent only. In this case the direction of the path makes an angle of about with the plane passing through the U-shape of the core.

Figs. 4 and 5 show a vertical section and a side-view respectively of an inductor 1 and a core 10, which fully surrounds the inductor on both sides. The core is H-shaped and comprises plate-shaped parts 11 on both sides of the inductor, so that better concentration of the lines of force is ensured.

A holder 12 for soldering material, for example tin wire 13, is united with the inductor to form an assembly, so that the soldering material is provided as a narrow tin band on the work-piece, for example, of white iron, when the work-piece 3 is moved in the direction of the arrow 14.

What I claim is:

1. A method for the local heating of a metallic workpiece by inductive high frequency heating with the use of an inductor including a U-shaped core having a high electrical resistance at high frequency comprising placing the free ends of the legs of said core in engagement with said work-piece to form a closed magnetic circuit, inserting at least a part of said inductor in the space between the legs of said core, moving the work-piece relatively to said core so that the heating zone on said work-piece constitutes a desired path, and providing said heated zone with soldering material applied along said heated path but immediately in front of said heating zone.

2. A high frequency inductor comprising a substantially U-shaped core positioned around said inductor and composed of a material having a high electric resistance at high frequencies, and a holder for a soldering element secured to said core.

3. A high frequency U-shaped inductor comprising a substantially H-shaped core composed of a material having a high electric resistance at a high frequency, said core being provided with two spaced plate-shape parts on each side of the inductor thereby enclosing said entire inductor and a connecting part in the space between the legs of said U-shaped inductor.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Magnetic Ferrites, New Materials for Modern Application, Electrical Engineering, August 1954, pages 726 729. 

